1. Field of the Invention
This invention relates to plastic processing machines, and more particularly to moveable screw arrangements for extrusion and injection molding.
2. Prior Art
Injection molding and extrusion employs the steps of hot working a plasticized or melted thermoplastic material and forcing same under high pressure into a mold or mold space, then allowing the material to cool sufficiently so that it hardens to the extent that it can retain its shape after removal from the mold or as it emanates from the mold.
During the plasticating process, it is often desirable to add a further processed material with the plastic material being worked within a screw housing. It is further desired to be able to add a solid, such as a pellet, wire, gas or a vapor, into the actual plastic material being molded or extruded.
Limitations of present plasticating screw machinery prevent the simultaneous introduction of a gas and/or a liquid, and or a vapor, and/or a solid, into that thermoplastic material as it is going into a mold or die.
It is therefore an object of the present invention, to provide a plasticating screw machine having capabilities not found in the prior art.
It is a further object of the present invention, to provide a screw machine which is able to present a solid and/or a liquid, and/or a vapor, and/or a gas, simultaneously or sequentially into a plastic being molded and/or extruded.
It is yet a further object of the present invention, to provide an arrangement which permits the rapid cooling and completion of a plastic part in a manner not found in the prior art.
It is yet still a further object of the present invention, to provide an extrusion and/or injection molding screw with multiple capabilities to mix and/or extrude and/or mold multiple components therewith in a manner not found in the prior art.
The present invention relates to a plasticating screw machine for treating thermoplastic material and pressurizably directing that thermoplastic material into an extrusion die or into an injection mold.
The plasticating screw machine of the present invention comprises an external barrel shaped housing having an elongated screw shaft rotatively supported therewithin. The housing and the screw shaft have a proximal or first end and a distal or a second end. The screw shaft is rotatively empowered at the proximal first end of the housing by a motor drive means thereattached. At least one material in-feed supply hopper may be arranged through the housing near the proximal end thereof.
The screw shaft has a bore extending completely therethrough along its longitudinal axis, from its proximalmost end to its distalmost end. The bore has a wall surface which may be rifled, that is, has a spiral groove cut within its surface, to define a material moving path.
A non-rotational sleeve support may bet arranged within the bore of the screw shaft, extending preferably from the proximal end of the housing, to the distal end of the shaft. A plurality of conduits may arranged within the sleeve support within the bore of the screw shaft. The conduits preferably extend out from the proximal end of the sleeve support, the conduits being in communication with any medium(s) such as a gas source, a vapor source, a liquid source, a or powder or solid source for feeding wire, pellets, powder, cooling fluid or the like into those conduits. The conduits have a distalmost end within the distal end of the screw shaft. The conduits may be held within a support baffle at the distal end of the sleeve. The sleeve support may be held in a bearing arranged within the walls of the bore of the screw shaft adjacent its distal end, for supportive carrying therein.
Each of the conduits may be moved longitudinally with respect to the screw shaft and or the sleeve support within the bore to advance its respective discharge end into any thermoplastic material as it emanates from the distal end of the housing. One or more of the conduits may be longitudinally advanceable through a die at the end of the housing, or into a injection mold at the distal end of the housing. The sleeve support may comprises a tubular member which encircles the conduit(s).
In a further preferred embodiment of the present invention, the entire sleeve support arrangement within the bore of the screw shaft may be longitudinally advanceable through the distal end of the housing, so as to present the delivery of any combination of medium(s) such as fluids, gas, vapors, and or solids such as wires, reinforcement fibers, optical glass and/or plastic at any location in or downstream of the plasticating screw and/or within the plastic being processed during the plasticating operation. Such medium(s) may permit the cooling, reinforcement, electrifying, lighting, softening, hardening, gasifying, hollowing or densification of any plastic being extruded or injected from the plasticating screw machine.
A further preferred embodiment contemplates a transfer of melted or fluid material along the annular path between the non rotatable sleeve support and the rifled wall of the bore within the screw shaft, to provide yet a further annular mixing chamber to the plasticating chamber between the flights of the elongated screw and the inner walls of the housing enclosing and supporting the elongated screw shaft.
A yet further preferred embodiment of the present invention contemplates the sleeve being rotatively disposed within the bore of the elongated screw shaft, either in a rotating or counter-rotating manner depending upon the direction of rotation of the elongated screw shaft itself. Such a rotating sleeve, would have a drive mechanism at its proximal end, in conjunction with a longitudinal displacement mechanism for advancing and retracting the sleeve longitudinally within the bore of the screw shaft, in a manner to permit any conduit therewithin to deliver and/or withdraw any single or combination of medium completely through the elongated screw shaft and or plastic being extruded and/or ejected from said screw and into a mold at the distal end of the plasticating screw machine.
In still yet a further embodiment of the present invention, when the screw shaft and associated internal conduits therethrough, are used in an injection molding operation, a mold may be utilized having an xe2x80x9cinarticlexe2x80x9d pin therewithin. The inarticle pin may be utilized to further supply and/or evacuate gas or liquids and/or powder from the injection mold. The inarticle pin may be retractably arranged within the mold, by a piston mechanism, which will move the pin from the mold itself. A fluid supply and vacuum line is in communication with the hollow inarticle pin and is in communication with a supply and discharge source, to permit such injection mold with a supply and vacuum means thereat.
Thus there has been shown, a unique screw construction or an injection molding machine or a plastic extrusion machine, wherein that same screw has a plurality of function transfer means included therewith. The separate conduits may be utilized individually or in combination, to continuously or sequentially add or withdraw a medium such as a vapor, a gas, a liquid, a foam, or a solid, into a plasticated material going into or through a die or a mold. The multiple conduits may be utilized to duct rearwardly excess gas, or vapor, or foam or liquid, or cooling material from the bore of the elongated screw shaft and/or support sleeve and/or tubular member therethrough, or mold, in conjunction with an inarticle pin arrangement or by themselves. If the screw shaft were to be used in the plastic injection format, the screw itself could be longitudinally advanceable and retractable towards a mold form.
The invention thus comprises a plasticating machine for the working and forcing of plastic material into a mold, said machine including an elongated housing having a first or proximal end and a second or proximal end, an elongated screw shaft with a screw flight therearound, the screw shaft being rotatably supported in the elongated housing, for the working of plastic between the screw shaft and the elongated housing, at least one delivery conduit generally longitudinally arranged through the screw shaft, from a proximal end to a distal tip end thereof, the screw shaft arranged to be movable with respect to the screw shaft to permit delivery of a medium through the screw shaft to any plastic being driven from the machine. The medium may be any single or combination of components selected from the group comprising vapor, liquid, gas, powder or solid.
The delivery conduit is movable longitudinally with respect to the elongated screw shaft. The delivery conduit is supported within a conduit support within a bore through the elongated screw shaft. The delivery conduit has a supply duct arranged on its proximal end, to supply said medium to the conduit for distribution of the medium into any plastic being delivered to a mold adjacent the distal end of the screw shaft. The conduit support may enclose a plurality of conduits therein, for the supply of a plurality of mediums to any plastic being delivered to a mold adjacent said distal end of the screw shaft. Each of the conduits in the plurality of conduits may be arranged parallel to one another. Each of the conduits in the plurality of conduits may be arranged coaxial with one another. At least one of the conduits may be arranged to carry a vacuum, to return a medium from the distal end of the screw shaft to the proximal end thereof. The conduit support may comprise an elongated sleeve. The elongated sleeve may be movable with respect to the elongated screw shaft. The elongated screw shaft may include a central bore therethrough from a proximal end to a distal tip end thereof, which central bore may have a grooved rifling therethrough, to assist in the movement of any medium passing through the bore itself. At least on of the conduits may be arranged to carry a cooling fluid therethrough, so as to provide a temperature control to any medium traveling thereadjacent. The elongated screw shaft may be movable longitudinally with respect to the elongated housing in which it is supported, to allow injection of plastic material from the housing into a mold thereadjacent. The mold may comprise a hollow injection mold. The conduits may be longitudinally advanceable and retractable with respect to the mold, to permit a medium to be delivered and/or withdrawn from any plastic supplied to the mold.
The invention also comprises a method of supplying a plastic to a mold for the manufacture of a plastic part therefrom, including the steps of providing an elongated rotatable screw shaft within an elongated barrel housing, the housing having a mold adjacent a distal end thereof, arranging a longitudinally directed bore through the elongated screw shaft from a proximal end to a distal end thereof, fitting at least one delivery conduit through the bore, so as to permit a medium to be directed through the screw shaft to any plastic being delivered to the mold adjacent the distal end of the housing, and attaching a medium supply duct at the proximal end of the proximal end of the conduit to permit a medium to be delivered through the conduit through the screw shaft and to a plastic part being generated at the distal end of the housing. The method may include the step of moving the delivery conduit longitudinally with respect to the screw shaft, to permit controlled delivery of the longitudinal location of any medium with respect to the screw shaft and the mold thereadjacent. The method may include the step of arranging a plurality of conduits within the bore of the elongated screw shaft, to permit the delivery of a plurality of mediums therethrough, to allow any plastic driven from the housing to be mixed with and/or treated by the mediums. The method may include the step of supplying any medium to the proximal end of the conduits, selected from the group comprising: a vapor, a cooling gas, a heated gas, a liquid, an optical fiber, a reinforcing fiber, an electrical conductor, and electrical resistor.